In the past year, research on the cellular function of ets-1 has focused on the role of ets-1 in astrocyte signalling and differentiation. Progress has been made in three major aspects: 1) analysis of ets-1 phosphorylation in response to transmitters in primary astrocytes, 2) identification of kinase inhibitors which block ets-1 phosphorylation in vivo, and 3) characterization of the effects of ets-1 transfection on P19 cells and on retinoic acid-induced differentiation of these cells along the neuronal and astrocyte lineages. Cleveland mapping studies comparing ets-1 from primary rat astrocytes, human astrocytoma, and human T-cell lines reveal identical sets of peptides. In primary astrocytes, the transmitters glutamate and norepinephrine were found to trigger phosphorylation of ets-1. Inhibitors of myosin light chain kinase block ets-1 phosphorylation in response to agonists and Ca++ ionophore and also block the previously described hyperphosphorylation of ets-1 in mitotic cells. P19 cells transfected to constitutively express ets-1 display morphological alterations resembling early stages of retinoic acid-induced differentiation. Work is continuing in each of these areas.